Here is another write-up on how to retrofit the 02-03 WRX headlights with HID (high intensity discharge) projectors. I read up (a lot) on the subject before starting my retrofit, so everything went remarkably smoothly. Overall, it wasn't very difficult. This write-up is intended as a stand-alone how-to, and I hope to highlight some of the areas of confusion regarding HID retrofits. That said, here is my obligatory disclaimer that I won't take any responsibility for a botched retrofit on your end. Happy retrofitting.

Output / before-after shots posted at the end..

Motivation:
There are plenty of preachy threads online about how bad it is to use cheap ebay HID kits in a standard halogen projector headlight. To summarize, the HID bulb is physically different in design than a halogen bulb. When you put an aftermarket HID bulb into a standard halogen headlight assembly, the light from the HID bulb is not properly reflected off of the halogen reflector bowl and the result is scattered light. This results in poor visibility despite a fairly bright-looking light. More importantly, it blinds oncoming traffic because of the non-uniform scattering of the light. The degree to which the light is scattered varies from car to car, but the bugeye WRX's stock housings are particularly bad at focusing light from an aftermarket HID bulb. Despite this, I had been using the cheap HID kit that came on my car for quite some time. I only recently made the decision to do a retrofit when my ballasts started to crap out.

Parts:
The theme of this retrofit was plug'n'play. I really wanted to do this retrofit, but I wanted it to be as simple as possible. For that reason, I went with the Bi-xenon Morimoto Mini Stage III Kit (H1) from TheRetrofitSource.com available here:

The Morimoto Mini H1 projectors combined with the adapter plates are designed to be installed with no modification to the stock headlight housing. This was not the case, however, and some minor modding is required (Scroll down to see what I mean).

For the 02-03 WRX, the options selected were:

Adapter Plate: 9007 (Doesn't really matter - These weren't used)

Ballasts: Morimoto 3Five (35W)

Bulbs: Morimoto 3Five 5000K

Projectors: LHD (North American Standard)

Re-Sealing Glue: Yes (+$10) (But I didn't end up using it)

Shrouds: Ocular

Wire Harness: Relay: 9007/9004

This kit was truly a complete kit. I did not need to purchase any additional wires/connectors/screws/etc... +1 for theretrofitsource.com

The complete package:

In addition to the functional pieces provided in the kit, I also bought:

Krylon Fusion Paint - Satin Black

Blue Painter's Masking Tape

in order to paint the housings.

Tools Needed:
There aren't any special tools you need to complete this project. Basics include:

Flathead

Philips

8, 10, 12 mm sockets w/ ratchet

An oven, or a heatgun

A Dremel rotary tool with cutoff wheels

On to the Retrofit

The first step is removing the headlights. You will need to take off the grill first. This can be done with just the flathead screwdriver by pushing down and releasing the (4) clips on the top and the (2) clips on the bottom:

Then remove the side grill pieces on either side of the grill by using the flathead screwdriver to pop out the (3) snap fasteners on each piece. There are two that are easily accessible from the top, but there is one on the bottom that you might miss if you you aren't careful.

Now, you can remove the headlights. They are held on by (3) 10mm bolts. Remove them.

Be careful when pulling out the headlight assembly. It can be tricky, and there is an additional "tab" that you can't see from the front of the light. By wiggling it side to side, you can slide the tab out from the housing and remove the headlight assembly. I may be wrong, but I think this is the "tab" people refer to when selling used headlights that often have "broken tabs." In other words, I assume they're easy to break if you're not careful.

Tab:

Tab "housing"

Once you wiggle both headlights free, unplug the turn signal harness and the main harness to fully remove the headlights.